Pen cap



FIG. 1 is a bottom front perspective view of a pen cap showing my new design;

FIG. 2 is a right side elevation view thereof, with the left side elevation view being a mirror image of the right side elevation view;

FIG. 3 is a front elevation view thereof, with the rear elevation view being a mirror image of the front elevation view;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof. 

CLAIM The ornamental design for a pen cap, as shown and described. 